The proposed projects are directed towards: a) The synthesis and the investigation of the physical and chemical properties of adenosylcobalamin, substituted with cysteine and ethanolamine. b) The electron spin resonance analysis of the free radical intermediates of adenosylcobalamin, labeled with 15N in the 5,6-dimethylbenzimidazole moiety. c) The chemical synthesis of 2 prime-13C-ATP and 2 prime-2H-ATP. d) The chemical synthesis and coenzymatic properties of (14CH3, 5 prime-3H2) S-adenosyl-methionine. e) The purification and characterization of ribonucleotide reductase from Corynebacterium nephridii. f) The purification and characterization of ribonucleotide reductase from Thermus X-1. g) The purification and characterization of thioredoxin and thioredoxin reductase from Corynebacterium nephridii.